Heretofore it has been proposed to employ microwave radiation either from microwave devices on the earth's surface or disposed in a wellbore in the earth to heat a hydrocarbonaceous fluid containing reservoir and the hydrocarbonaceous fluid itself to render the fluid more mobile and therefore, more easily produced from the reservoir formation into a wellbore for production to and recovery at the earth's surface. Such microwave heating techniques and the apparatus necessary for practicing same are well-known to those skilled in the art, see U.S. Pat. No. 3,170,519 issued Feb. 23, 1985 and U.S. Pat. No. 4,193,448 issued Mar. 18, 1980.